Bump nix version to fix build on nightly
Bump nix version to fix build on nightly

fhartwig/mio,echochamber/mio,pythonesque/mio,rrichardson/mio,greensnark/mio,zslayton/mio,carllerche/mio,bottompawn/mio,fuchsia-mirror/third_party-mio,luca-barbieri/mio,mneumann/mio,alexcrichton/mio,mneumann/mio,yangxingpping/mio,mlalic/mio,carllerche/mio,murarth/mio,tempbottle/mio,asomers/mio,thijsc/mio,geofft/mio,frewsxcv/mio,danburkert/mio,dwrensha/mio,dpc/mio,tailhook/mio,marjakm/mio,arthurprs/mio,hjr3/mio,rryan/mio,yuikns/mio,fuchsia-mirror/third_party-mio,asomers/mio